Grinding head



L. STETLER GRINDING HEAD Oct. 26, 1943.

Filed Aug. 4, 1940 2 sheets sheet l Iuvsu roR Lowsu. S-renen STETLER GRINDING HEAD Filed Aug. 4, 1940 WIIII I 2 Sheets-Sheet 2 Patented Oct. 26, 1943 UNITED STA we I Stetler, Cleveland, pine, assignor; by

to Samuel '1. Haas, Clevemesne assignments, I land,'Oh 1o p A Application August 4, 1940, Serial NoL 351,333

g 1, 10 Claims.

This invention relates to a grinding head, and; more particularly, to a grinding head adapted to grind off a given depth'of material from all portionsof an undulating surface, such as, for example, the warped surface of a'slate blackboard. A grinding head made according to this invention is especially adapted for performing the preliminary grinding operation in my methoolof dressing slate described in my co-pending application No. 345,737. I

Grinding heads, heretofore, have not been completelysatisfactory in that they tended to grind off only the high spots when applied to warped surfaces and'also tended to scarify the surface being ground. In the grinding heads used heretofore, abrasive sheets, suchas sandpaper, were not generally used successfully because the grinding heads wore vout the sheets-veryquickly, the sheets were secured to the grindinghead with difliculty, and the manner of cutting the abrasive sheeting to fit the grinding heads was wasteful.

It is an object of-this invention to provide a grinding head which will grind the required amount of material off'the low spots as well as off the high spots-of a warped surfaceby providing three resilient sled shaped grinding'sectors located at the periphery of alight'grinding disk floatingly'mounted on the driving shaft. It is also an object of this invention to provide a grinding head which will not score the surface being ground by suitablylocating and proportioning the grinding sectors andalso byproviding means to conduct heat rapidly away from the abrasive surfaces. In the preferred embodiment of my invention particles of grit loosened from the abrasive sheeting willnot be scratched. into the surface being ground.

It is a further object of this invention .to provide a grinding head which will prolong the vlife of the abrasive sheeting employed by rapidly conducting the heat away fromtheabrasive sheeting. It is another object of thisinvention to provide a grinding head which will permit the abrasive sheeting to be quickly and conveniently se- I cured thereto. It is a still further object of this invention to provide 'agrindin'g head which will permit the sectors of abrasive sheeting to be cut economically and conveniently.

Otherand further objects and-advantages of this invention will. be apparent from the following specification, claims, and drawings in which: Fig. 1 is a front elevation of the grinding head.

Fig. 2 is a fragmentary detail section taken along the line 2-2 of Fig. 1. a 1

' Fig. 3 is a detail showing the manner 'ofcutting abrasive sectors from an abrasive sheeting.

Fig. 4 is afragmentary detail section taken along the line 4-4 of Fig. 1. 1 Fig. 5 is a'detail elevation of a sector plate shown in section in'Fig. 4. v I I In the drawings, in which like reference characters refer to like parts, II represents thedisk of the grinding head I0. In order to obtain the required rigidity and strength with minimum weightQthe disk- I I is preferably made of ply wood reinforced by the rim I2.

The grinding head II] is driven-by the driving shaft I3 through a hub I4 which permits the disk I I to float with an angular movement which is substantially centered on the axis of the driving shaft I3. The hub I4 is comprised of a disk plate I5 which is received and" suitably secured, ;by a force fit, for example, in the face of the disk II and is removablysecured to the shaft I3 by'the stud bolt l6. The disk plate I5 carries the evenly spaced integral driving pins II which are loosely engaged'inthree of thesix holes I8 of the'fiberdriving ring I9. Ashaft'plate 20,

- carried by the shaft I3, is provided with three evenly spaced'integral driving pins 2 I which are loosely received in the remaining holes l8 of the driving ring I9. Alive rubber bushing 22 is fitted between the shaft pilot 23 and the bore of the driving ring I9 and is partly compressed between the plates I5 and 20. The bushing122 tends to maintain the disk II at right angles to the shaft I3 but due to the loose fit between the driving pins I1 and 2| and the holes I8 of the driving'ring, the disk II can be wobbled as it is driven by the shaft I3; I

Evenly spaced about the periphery of the disk II are three grinding sectors 25, the arcuate length'of each preferably being approximately one-sixth of the circumference of the disk II.

'By so spacing and arranging the sectors 25 on the angularly movable disk I I, the grinding sectors 25 are sure, within the limits of theWobble-permitted by the hub I4, to engage all portions of a warpedsurface to be ground. Also, by providing ample space between the sectors 25, the surface being ground is less likely to become overheated. The radial width of the sectors 25 is preferably less than one-third of the radius of the disk II. By sopropo rtioning the width of the sectors,

"there is no tendency to score the surface being ground due to the differential peripherial speeds between radiallyspa'ced'portions of the abrasive, and, further, particles of abrasive which may break off the sectors will be quickly thrown off by in configuration .to the snap and be F 1 g i d n ira i iQQite .t e-.e i e i jres nin whi t a ra v centrifugal force and will not be scratched into the surface of the material being ground.

As shown in Fig. 4, each abrasive sector 25 is comprised of a sector plate 26 secured at its radially extending edges to the disk H. As shown in Figs. 4 and 5, the radially extending side edges'of each sector plate 26 are provided with acute angular flanges 2] whichextend over the side margin of the plate? Betwee'rf-itsside' ar;

gins the "plate 26 is provided with a"plura1ity' of pin holes 28. An opening 29 is cut through the disk i I beneath the pin holes 28. 1

A resilient pad 30 of sponge rubber or the-like is located between the flanges 2'1, the central portion of the pad 30 being raised welliabov t-h flanges 21, from which central "portion 'the pa slopes toward the flanges so that the pad 30 is sled shaped through its longitudinalg sectiqnz A plurality of pins 3| are embedded in the pad 30 and extend from the curved upper surface "of" the; pad-through. the. ,pin holes .23 and opening 2 p etall c rinsr la 3 gauge spring brass orfsprin the :pad 2. t ds: ti engaged in the flanges 2.1 I posit n-w.-

tors '3.3 of..ab. a e.; sheen referablyhin le sfitte gfver. -R ne l t bei secure the plate in Q I P lQ i the ind ng SEQ Q iN are c t: rom she p i able abra: ivesheetina. su h. assand ape M ,s ?i shown in Fig. 3. Because the arcuateshape oi the abrasiveseotors 333 permit the patterngto be n sted, @the. amou v f. Wastei heet ne; is very small anduthecos eoi t e.. e 0r s-redu tore mi-nimumr The abrasive. sectors 33 are secured inthegrindingsectora -25bit simp y. s p n th ends of: thesheets etweenthe nds. f-th i sprin plate 3 2;.and the ;flanges;-21;, Although the abrae sive sectors 33 are. thus pnly. friotionally enga ed inlrthe grinding sectorsfiand; consequently. may :beis'readily removed and replaced. thei;abrasive sectorsxdog notzbecome. dislodged under load. -It

.is'. believed -;that the. reason for, the. abrasive-sees:-

,tors.; bei-ng effectivelysecuredsduring usez-zisjthat K I the pressure on. thegrinding sector 25, which-dis.- -tOIfiSxt-h8 springplate.32,.-.causes"thetspring;plates :to edge theeabrasive-ssectorsz33 into the zfianges 'tated' ,'-and .trans1ated over the surface; .being ground. The spring plates 3'2, -'supportedabyp .the

resilient pads, v 3 t permit the. individual .grinding sectors 252t0 accommodate Lthe minor; variations in the" r a e n ero ndh e a e f th r nd s tor 5 pe t h m; to p s :QYer, and grind. down ,sudden chan ges .inthesurf .ace being ground. such as. cracks, hard yeins,

125 has he nie ilqipi i .frh n n siste m ked eer a ve sheeting to.

th .lm t nra edt x ds t is messesigma pa t c l @n v r m th a eetin he b eem were. o a d thei etsr -Q scares the sur e bei gro nd n the. in in ec.-

It i igh w 'et t e h tenera d in. theabrasiveflsectorsfi i sr i lybo d t dt he brine it as vsii n tedi.;bv; .the

lII'elJhB huh I 4 permits the t'g-rindingnhead'lilll .to accommodate itself to-the larger. undulations. of a .Warpedsurface, so. that :all three;- of the; grinding sectors 'are' engaged as the grinding v heaclr l ii lisv simultaneously: 1:0.-

.14.: In a...sri d a-headfadr vir esha t,Bern I ,a driving connection betweensaid shaft andsaid disk permitting said .disk to, wobble when driven ing pad to the sector plate 26 and to the air in the opening 29. the abrasive sector 33 may thus be maintained below the softening point of adhesive in which.

the grit is embedded without having to slow the grinding head Ill below an efiective grinding speed. Thus, scoring is reduced and the abra sive sheeting need be discarded onlywhen the grit isworn down and not because ytheggrit is lost.

Ha Ving disclosed a "preferred embodiment of this invention, it is not to be understood that this invention is limited to the specificembodi mentdisclosed, either in whole or in part, but

islimited only by the appended'claims.

Whatis claimedisi: w

lna 'grindingshead of the'class described, a. disk, a drive -shaft} a disk plate secured to said dislg driving .pins-on said disk plate, a shaft plate" mounted on saidshaft, driving pins on said sl'iaft plate, a driving ring loosely engaged between said disk. plate and w said shait .plate 't' 1 ai 'el' a saidsetor plataa'resilient t mounted;

ewnate thec t el on-1 o t n ngabove id flan es en hgmr i g tions. inez pe 'tqwa dz aid flan es.- a s12 plate e ten in ver. aidnad;as iorlo abxe s eet n s ppo t d by 'saids in .plateand cured ine aid. fl n es ;,and pinswex e ldlna" th ou h sa drp d mmt dq n in 'p t w id sector.:;plate.--;. 1 1. Ina rind-in ,eadu. ucomb na n disk. a: d ive shaf i k. p te.) ecur ditm coupling means connecting said shaftiplatesto said disk platerto permit said disk; plate :tozwobble' within the; limit :of looseness -.of-;:-said ;coupllng .whenldri-ven bysaidshaft;andacresilientvbushr in' x, supporting i; said disk. .on: said shaft- 5 ithree equally; spaced; :grindingxsectors' disposed about .the periphery of; said idiskaeacnpf s'aidse'ctors :comprisinga resilientarcuate pa'd having'a raised central portion andzsloping marginal portionsiia I spring.plate-extending over said pad,v afsectorxof 'abrasive sheeting, andflanges permitting rsaid "1" :sector of abrasive sheeting to be secured b'etwen :said spring plate and said fianges; ;:i '17 ';:13.ln a' grinding head; the combination ofi-a vdislgra" drive' shaft, a disk. platei 'secureditoasaid disk, a. shaft plate: secured: worsen shaftg loo'se coupling means connectingi saidshaft- 'platei to said diskplate to permit said-tdisk plate to wobble within the! @limit of loosen'essr of said; coupling "when driven! by-said'shaft; and a resilient-bush ingasupporting; saidi disk on. said. shaft;:,three equally."spaced'grinding sectors disposed. about the periphery of. l said kdisk, .each'; of 3 said sectors .eomprisingasector ,plate,-a spring plate;;extend:-' 'ing across-.said-sectorgplate and engagedzthereon so: that i th .c ntra1,.portion :of .-sa d-:-sprin plate ,1 is; raised above; rther-marginalx; DQItiOnS's" aid plate, a sector of abrasive sheeting 'slupportedp'by s i pri ep1ate, and m ans n m t ney id sector of; abrasive :sheeting cured to. saidvdisk.

The temperatureof i v aid-, f I ..d,isk,.;-a.shaft-plate,securedgtosaidshaft. loose by said shaft, three grinding sectors equally spaced about the periphery of said disk, the arcuate length of each grinding sector being not more than the arcuate spacing between adjacent grinding sectors and the radial depth of each grinding sector being not more than one-third of the radius of said disk, and each grinding sector comprising an arcuate sector of abrasive sheeting, a springeplatesupporting said sector of abrasive sheeting, the central portion of said spring plate being elevated above the marginal portions thereof, and means for removably securing said sector of abrasive sheeting to said disk.

5. In a grinding head, a driving shaft, a disk, a

driving connection between said shaft and said disk permitting said disk to wobble when driven by said shaft, three grinding sectors equally spaced about the periphery of said disk, the radial depth of each grinding sector being not more than one-third of the radius of. said disk, and each grinding sector comprising an arcuate sector of abrasive sheeting, a spring plate supporting said sector of abrasive sheeting, the central portion of said spring plate being elevated above the marginal portions thereof, means for removably securing said sector of abrasive sheeting to said disk, and means for conducting away and dissipating the heat conducted from said section of abrasive sheeting to said spring plate.

6. In a grinding head, a disk, three equally spaced arcuate sectors disposed adjacent the periphery of said disk, the arcuate length of each grinding sector being not more than the spacing betweenadjacent grinding sectors and the radial depth of each sector being not more than onethird of the radius of said disk, each grinding sector being comprised of an arcuate sector of abrasive sheeting, resilient means for supporting] ate sides,'said pad having a raised central portion and a marginal portion slopingtoward an end of the pad, a spring plate extending over said pad, a sector of abrasive sheeting supported by said spring plate, means for securing said sector of abrasive sheeting and causing said spring plate to conform to the profile of said pad, and means for dissipating the heat generated by said sector of abrasive sheeting through said a 8. In a grinding sector for a grinding head, a resilient rubber pad having arcuate sides and ends radially disposed with respect to the arouate sides, said pad having a raised central portion and amarginal portion sloping toward an end of the pad, a sector of abrasive sheeting, means for securing said sector of abrasive sheeting and causing said sector of abrasive sheeting to conform to the profile of said pad, and means for dissipating the heat generated by said sector of abrasive sheeting through said pad.

9,. In a grinding sector for a grinding head, a resilient spring plate having an arcuate outer 'side and ends radially disposed tosaid side, a

sector plate.

sector of abrasive sheeting supported by said spring plate, means springing saidspring plate so that the central portion thereoflwith respect to its outer side, is elevated and a marginal'por tion thereof slopes toward an end of the spring plate, said means also permitting said sector of abrasive sheeting to be removably secured in a heat-conducting relationship to i said spring plate.

' 10. A grinding sector for a grinding head comprising a disk, a perforated sector plat extending over an opening in said disk, acute angular flanges extending along the radial edges of said sector plate, a resilient pad mounted on said sector plate, the central portion of. said pad extending above said flanges and the marginal portions being sloped toward said flanges, a spring plate extending over said pad, a sector of abrasive sheeting supported by said spring plate and secured said flanges, and pins extending through said pad from said spring plate to said LOWELL STE'I'LER. 

